Conventional Semiconductor Processing Research Articles

Electrohydrodynamic Printing‐Based Heterointegration of Quantum Dots on Suspended Nanophotonic Cavities

AbstractNanophotonic structures are a foundation for the growing field of light‐based quantum networks and devices enabled by their ability to couple with and manipulate photons. Colloidal quantum dots (QDs) are uniquely suited to complement this range of devices due to their solution‐processability, broad tuneability, and near‐unity photoluminescence quantum yields in some cases. To bridge the gap between them, electrohydrodynamic inkjet (EHDIJ) printing serves as a highly precise and scalable nanomanufacturing method for deterministic positioning and deposition of attoliter‐scale QD droplets. This includes heterointegration in devices that are challenging to create by conventional subtractive semiconductor processing, such as QDs emitters coupled to substrate‐decoupled nanoscale resonant structures. In this work, the first successful application of EHDIJ printing for the integration of these colloidal QDs into suspended nanophotonic cavities is demonstrated, achieving selective single‐cavity deposition for cavity pairs as close as 100 nm apart. These results motivate the development of future suspended hetero‐integrated devices that utilize EHDIJ printing as a sustainable, additive, and scalable method for quantum photonics nanomanufacturing.

Flexible Artificial Mechanoreceptor Based on Microwave Annealed Morphotropic Phase Boundary of HfxZr1‐xO2 Thin Film

AbstractThe development of artificial tactile receptor systems is important in the fields of prosthetic devices, interfaces for the metaverse, and sensors. A pressure sensor and memory device may be used in this system to replicate the tactile detecting capabilities of human skin. The implementation of systems that take into account mass production and miniaturization is still difficult. Here, a flexible artificial tactile receptor built using conventional semiconductor processes that combine a vertically stacked piezoelectric sensor with neuromorphic memory is presented. As a fundamental component for both sensors and memory, hafnium zirconium oxide (HZO) formed by using semiconductor deposition technique is introduced. Due to its exceptional piezoelectric performance, the morphotropic phase boundary of HZO is studied. The entire materials and processes are highly compatible with conventional semiconductor processes, including microwave annealing‐based low‐temperature crystallization. Even after 10,000 times of bending stress, the sensor and memory constructed on a flexible substrate exhibit consistent pressure detection characteristics over a wide range of 2–25 kPa. The feasibility of the approach is further demonstrated by a deep neural network simulation, which reached 90.8% braille recognition accuracy. Wearable electronics and medical devices are two examples of industrial domains that can use these flexible, exceptionally durable devices.

(Invited) Integration of Functional Nanostructures and Nanoparticles into Micro- and Nanoelectronic Components and Systems

In recent decades, there has been a significant evolution of microelectronic and semiconductor technologies towards the nanoscale. Both bottom-up and top-down integration concepts of functional nanostructures and nanoparticles into micro- and nanofabricated electronic components have become critical issues that decisively affect the performance of smart electronic systems in various application areas such as environmental sensing and energy harvesting.Functional nanostructures and nanoparticles of different shapes, sizes, morphologies, and materials are now used in various technical and industrial applications, medicine, pharmacy, biology, electronics, power engineering, ecology, and many other fields. However, the complex engineering challenge here is the integration of functional nanostructures, such as molecular components (e.g., functional self-assembled molecular monolayers or entities of desoxyribonucleic acid, DNA), organic or inorganic nanoparticles (metal, semiconductor, colloidal materials), or similar building blocks into nanolithographically fabricated environments.Manufacturing paradigms for this integration go beyond current CMOS- and MEMS-fabrication schemes. Scale-bridging and hybrid manufacturing schemes that combine established top-down manufacturing techniques for microelectronic devices, including aspects of nanotechnology, with bottom-up nanoassembly of molecules on unstructured and pre-structured substrates are required. Microsystems technology based on the combination of conventional semiconductor processing with biotechnological approaches has thus become an emerging field with manifold applications, especially in the field of sensor technology.This contribution describes two illustrative and innovative research questions in nanopatterning and system integration at the micro-nano-interface to motivate applications with new and unprecedented functionalities. The first research question focuses on network-based biocomputing (NBC) using biological agents driven by biomolecular motor proteins in a lithographically fabricated nanofluidic channel system. This approach opens up opportunities for energy-efficient solutions to complex mathematical problems as they make their way through the NBC network. Methods are required to create switchable and rewritable nano-networks to address different mathematical problems using a single NBC-chip. Therefore, stimuli-responsive materials must be selectively and locally deposited into the nano-network to control the transport of the filaments through the network.The second research question focuses on nanophotonic devices based on DNA origami. The high-precision arrangement of nanoscopic substructures using specific binding sites (capture ends) of the DNA origami enables the precise arrangement of DNA origami functionalized with individualized metal nanoparticles. This arrangement could be used to exploit individual spectral response mediated by plasmonic effects.From a technological perspective, top-down lithographic nanostructuring technologies and bottom-up nanostructuring technologies are the basis for new device concepts. The adaptability of nanostructures to the world of biological molecules and other nanoscopic building blocks such as quantum dots and nanoparticles enables novel, even personalized, devices and engineering solutions.

Hydrogen Fluoride Gas Sensor by Silicon Nanosheet Field-Effect Transistor

Chemical sensors are an essential part of modern society to ensure safety, from preventing pollution to saving lives. Especially, the demand for real-time monitoring of hydrogen fluoride (HF) increases continuously due to its high toxicity, contrary to its wide use in industries. In addition, compact size and low cost are favorable to utilize the sensor in wide spreading applications in industries. Herein, we present a compact HF gas sensor with high sensitivity and selectivity. The HF sensors, fabricated in the form of field-effect transistors (FETs) using a cost-effective and mass-production friendly conventional semiconductor process, are shown to possess good electrical characteristics enabled by a silicon nanosheet (SiNS) current channel. High sensitivity on gas phase HF is achieved by the unique catalytic sensing membrane -- platinum/polycrystalline lanthanum fluoride (Pt/poly-LaF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ). The high responsivity ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> ) of 3,071% at 25 ppm and the low limit of detection (LOD) of 219 ppb were achieved at room temperature (RT), along with a quick response time of 5.56 minutes which are crucial for the workplace environmental safety. The developed HF sensor can be a potential candidate for the industrial mobile sensor platform.

Flexible Amorphous Indium-Gallium-Zinc Oxide Thin-Film Transistor with Aluminum Oxide Gate Insulator on Polyimide Substrate By Spray Pyrolysis for Foldable Display

Research interest in thin-film transistor (TFT)-based flexible electronics for next-generation foldable and rollable displays is increasing, centering on flexible plastic substrates such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyimide (PI). For flexible electronics using plastic substrates, it is important to select suitable semiconductor materials that can be deposited at low substrate temperature. Metal oxide (MO) semiconductors such as indium-gallium-zinc oxide (IGZO), zinc oxide (ZnO) are attracting attention as suitable candidates for plastic substrate electronics because of their higher mobility and optical transmittance than hydrogenated amorphous silicon (a-Si:H). In addition, since it can be processed at a lower temperature than low-temperature polysilicon (LTPS), it can be easily applied to flexible plastic substrates. One of the greatest advantages of MO is that it can be easily fabricated by conventional semiconductor processing methods such as sputtering, atomic laser deposition, and solution processes. Among them, solution-processed deposition method is particularly advantageous in terms of manufacturing efficiency because it does not require a separate vacuum system, and can efficiently utilize raw materials, so the fabrication cost is inexpensive. In particular, spray pyrolysis can guarantee environmental stability, high mobility, and large area production than other solution processes. In this work, we developed the high-performance, flexible a-IGZO/Al2O3 TFTs using spray pyrolysis fabricated on the flexible PI substrate. In a previous study, we developed a method to reduce curling and electrostatic discharge (ESD) damage to PI substrates by using a mixture of carbon nanotubes (CNTs) and graphene oxide (GO) between carrier glass and PI substrate. Therefore, it was possible to mechanically detach the TFTs on PI substrate and handle them easily even after detachment. The spray-pyrolyzed Al2O3 film is one of the high-k dielectric materials, which can lower the operating voltage, so the low-power consumption of the TFT backplane can be realized. The flexible spray-pyrolyzed a-IGZO/Al2O3 TFT exhibits the field-effect mobility (µFE) of 9.75 cm2 V−1 s−1, threshold voltage (VTH) of −0.8 V, subthreshold swing (SS) of 0.29 V dec−1, and on/off current ratio of 6.2 × 107. Even without TFT passivation layer, it shows environmental stability. The TFTs show robust electrical performance even under tensile strain with a bending radius of 1 mm. In addition, it showed stable electrical characteristics even in the repeated bending test of 30,000 cycles under compressive strain with a bending radius of 1 mm. This is due to fewer defects resulting from the smooth interface of the a-IGZO film and the Al2O3 film deposited through spray pyrolysis. Therefore, spray-pyrolyzed a-IGZO/Al2O3 TFT fabricated on PI substrate is a promising candidate for next-generation foldable display application. Figure 1

Superconducting and Silicon-Based Semiconductor Quantum Computers: A review

Quantum computers are based on the theory of quantum mechanics, and their powerful parallel data processing capability is expected to solve many mathematical problems that too are difficult to be handled by classical computers. Especially with the increase of data processing volume, the quantum advantage is more obvious. Among the many physical systems for quantum computers, superconducting quantum circuit and semiconductor quantum dot computers show amazing potential due to their compatibility with traditional integrated circuit process technology and ultrashort gating time of nanoseconds. Superconducting qubits consisting of Josephson junctions and superconducting coplanar capacitors are easily integrated into a large scale for their simple circuit structure and conventional semiconductor process compatibility. Semiconductor qubits made from isotopically purified silicon (Si)-based materials greatly suppress nuclear spin noise, and decoherence times of ultralong milliseconds can be achieved. In this article, we systematically describe the challenges faced by superconducting qubits and semiconductor qubits in hot issues such as error correction and decoherence and look into the future development of superconducting quantum computers and Si-based semiconductor quantum computers.

Directed high‐χ block copolymer self‐assembly by laser writing on silicon substrate

AbstractPolymer self‐assembly commonly suffers from retarded equilibrium structure formation caused by the large diffusion barrier of long‐chain molecules. In particular, the defect annihilation kinetics of high‐χ block copolymers (BCPs) are generally sluggish because of a slow inter‐block chain diffusion process from strong inter‐block segregation. Therefore, long‐range order of high‐χ BCPs still hard to be obtained by conventional approaches. Here, we introduce near‐infrared laser photothermal treatment to effectively promote high‐χ BCP self‐assembly and demonstrating highly aligned nanoscale patterned structures on silicon substrates. Adequate molecular weight selection of high‐χ PS‐b‐P2VP system enables one‐time laser hot‐zone annealing, resulting in highly ordered nanodomains along laser writing direction. Facile sub‐sequential metal ion loading to P2VP cylinders enables the formation of highly aligned metal nanowires. Moreover, a commonly used silicon substrate without a photoabsorbing layer is employed as a photo‐thermal substrate, demonstrating that the laser writing process is compatible with conventional semiconductor processes.

Recent Advances in Metal-Oxide Thin-Film Transistors: Flexible/Stretchable Devices, Integrated Circuits, Biosensors, and Neuromorphic Applications

Thin-film transistors using metal oxides have been investigated extensively because of their high transparency, large area, and mass production of metal oxide semiconductors. Compatibility with conventional semiconductor processes, such as photolithography of the metal oxide offers the possibility to develop integrated circuits on a larger scale. In addition, combinations with other materials have enabled the development of sensor applications or neuromorphic devices in recent years. Here, this paper provides a timely overview of metal-oxide-based thin-film transistors focusing on emerging applications, including flexible/stretchable devices, integrated circuits, biosensors, and neuromorphic devices. This overview also revisits recent efforts on metal oxide-based thin-film transistors developed with high compatibility for integration to newly reported applications.

Mapping Oxidation and Wafer Cleaning to Device Characteristics Using Physics-Assisted Machine Learning.

It is always highly desired to have a well-defined relationship between the chemistry in semiconductor processing and the device characteristics. With the shrinkage of technology nodes in the semiconductors roadmap, it becomes more complicated to understand the relation between the device electrical characteristics and the process parameters such as oxidation and wafer cleaning procedures. In this work, we use a novel machine learning approach, i.e., physics-assisted multitask and transfer learning, to construct a relationship between the process conditions and the device capacitance voltage curves. While conventional semiconductor processes and device modeling are based on a physical model, recently, the machine learning-based approach or hybrid approaches have drawn significant attention. In general, a huge amount of data is required to train a machine learning model. Since producing data in the semiconductor industry is not an easy task, physics-assisted artificial intelligence has become an obvious choice to resolve these issues. The predicted C–V uses the hybridization of physics, and machine learning provides improvement while the coefficient of determination (R2) is 0.9442 for semisupervised multitask learning (SS-MTL) and 0.9253 for transfer learning (TL), referenced to 0.6108 in the pure machine learning model using multilayer perceptrons. The machine learning architecture used in this work is capable of handling data sparsity and promotes the usage of advanced algorithms to model the relationship between complex chemical reactions in semiconductor manufacturing and actual device characteristics. The code is available at https://github.com/albertlin11/moscapssmtl.

Unidirectional transmission of funnel-shaped waveguide with complete bandgap

It will be a future trend to apply quantum photonic technology to communication technology and information processing. One of major developing directions of quantum photonic technology is the miniaturization and on-chip integration. Like the diodes in integrated electric circuitry, optical unidirectional transmitter devices (UTDs) play an important role in processing the quantum information and also represent the main components of integrated optical devices. Thus, the design of UTDs has become one of the research hotspots. With photonic bandgap and localization characteristics, as well as easy micro-nano scaled integration, the photonic crystals (PCs) are often preferred when used to develop micro-nano integrated optical devices. At present, the common methods of achieving UTD with photonic crystals include directional bandgap mismatch, asymmetrical coupling by a micro-cavity, odd-even mode conversion, total reflection of photonic crystals with grating and photonic crystal heterostructure, etc. However, these optical unidirectional transmitters gained through the above methods generally have a low forward transmission, narrow working band, complex structure, etc. In the paper a novel method of UTD is put forward based on photonic crystal and a UTD of funnel-shaped waveguide is designed. The design of the device is divided into two parts: optimal funnel waveguide design and optimal point defect design. The band structure of TE polarized photonic crystal is calculated by R-soft. A triangular lattice circular air hole photonic crystal with complete photonic band gap is used as the initial structure and line defects are introduced to form a funnel-shaped waveguide structure (FSWS). The FSWS consists of the first waveguide W1, the second waveguide W2 and a funnel cavity. The funnel cavity is shaped like a funnel and located at the coupling between W1 and W2. Owing to the unique characteristics of the waveguide, the light wave transmission will be localized in the waveguide, which is conducive to improving the forward transmission. The influence of width variation of W2 with forward and backward incident light are analyzed by the finite difference time domain (FDTD) method, and W2 is selected as a waveguide formed by removing 11 rows of air holes. The FSWS achieves the initial asymmetric transmission, while the backward transmission remains high. Further studies are conducted to introduce four types of point defects to suppress the backward transmittance. The point defects refer to moving one or two air holes. In the work the FDTD is also used to calculate four kinds of point defect backward transmittance spectra and optimize the positions of point defects. Finally, it is found that when the optimal point defect mode is type I and &lt;i&gt;d&lt;/i&gt; = 5&lt;i&gt;a&lt;/i&gt;, the forward transmission (&lt;i&gt;T&lt;/i&gt;&lt;sub&gt;f&lt;/sub&gt;) and transmission contrast (&lt;i&gt;C &lt;/i&gt;) at 1550 nm are 0.716 and 0.929, respectively. Working bandwidth (&lt;i&gt;B&lt;/i&gt;) can be increased up to 111 nm (1501–1612 nm). By mode analysis, it is found that the point defect introduces mode mismatch between W1 and W2, by converting the fundamental mode in W2 into high-order modes. Thus, the back-propagating light waves in W2 cannot effectively couple into W1, resulting in complete blockage of backward propagation. In addition, the structure is made of silicon based air hole photonic crystal. The 2D air-hole PC slab is mature and even compatible with conventional complementary metal oxide semiconductor (CMOS) processing. The designed UTD is easy to implement, and has the advantages of simplicity and high unidirectional transmission characteristics. Therefore, it can provide a new solution for UTDs with higher requirements for integrated optical path at present.

Femtosecond laser induced in-situ crystallization of Tb-based luminescent metal organic framework.

Luminescent metal-organic frameworks (LMOFs) are a class of interesting and well-investigated MOF materials, which have shown remarkable prospects in the past and have been widely applied in different fields. However, due to their organic hybrid aspect, micro-/nano-patterning LMOFs in devices via a conventional semiconductor process is very challenging. In this work, we have introduced an elegant technique via nonlinear photon-chemical effect to induce the synthesis and growth of LMOFs. A facile technique for local synthesis and micro-pattering Tb-based luminescent metal organic frameworks (Tb(BTC)·G) from a solution of precursors is achieved. A single step approach micro-patterning for device integration with simultaneous chemical synthesis was proposed. Micro-devices with excellent fluorescence performance based on Tb(BTC)·G have been demonstrated. This work first suggested a high resolution bottom-up micro-patterning technique for MOF device fabrication using femtosecond laser direct writing, showing great potential on MOF based micro/nano-devices integration, especially promising for patterning high resolution luminescent MOF devices.

Fully Bottom-Up Waste-Free Growth of Ultrathin Silicon Wafer via Self-Releasing Seed Layer.

The fabrication of ultrathin silicon wafers at low cost is crucial for advancing silicon electronics toward stretchability and flexibility. However, conventional fabrication techniques are inefficient because they sacrifice a large amount of substrate material. Thus, advanced silicon electronics that have been realized in laboratories cannot move forward to commercialization. Here, a fully bottom-up technique for producing a self-releasing ultrathin silicon wafer without sacrificing any of the substrate is presented. The key to this approach is a self-organized nanogap on the substrate fabricated by plasma-assisted epitaxial growth (plasma-epi) and subsequent hydrogen annealing. The wafer thickness can be independently controlled during the bulk growth after the formation of plasma-epi seed layer. In addition, semiconductor devices are realized using the ultrathin silicon wafer. Given the high scalability of plasma-epi and its compatibility with conventional semiconductor process, the proposed bottom-up wafer fabrication process will open a new route to developing advanced silicon electronics.

High Current Density in Monolayer MoS2 Doped by AlOx

Semiconductors require stable doping for applications in transistors, optoelectronics, and thermoelectrics. However, this has been challenging for two-dimensional (2D) materials, where existing approaches are either incompatible with conventional semiconductor processing or introduce time-dependent, hysteretic behavior. Here we show that low-temperature (<200 °C) substoichiometric AlOx provides a stable n-doping layer for monolayer MoS2, compatible with circuit integration. This approach achieves carrier densities >2 × 1013 cm-2, sheet resistance as low as ∼7 kΩ/□, and good contact resistance ∼480 Ω·μm in transistors from monolayer MoS2 grown by chemical vapor deposition. We also reach record current density of nearly 700 μA/μm (>110 MA/cm2) along this three-atom-thick semiconductor while preserving transistor on/off current ratio >106. The maximum current is ultimately limited by self-heating (SH) and could exceed 1 mA/μm with better device heat sinking. With their 0.1 nA/μm off-current, such doped MoS2 devices approach several low-power transistor metrics required by the international technology roadmap.

Silicon Shadow Mask Technology for Aligning and In Situ Sorting of Semiconducting SWNTs for Sensitivity Enhancement: A Case Study of NO2 Gas Sensor.

Single-walled carbon nanotubes (SWNTs) are incorporated in different device configurations such as chemiresistors and field-effect transistors (FETs) as a sensing element for the fabrication of highly sensitive and specific biochemical sensors. For this purpose, sorting and aligning of semiconducting SWNTs between the electrodes is advantageous. In this work, a silicon shadow mask fabricated using conventional semiconductor processes and silicon bulk micromachining was used to make metal contacts over SWNTs with a minimum feature of 1 μm gap between the electrodes. The developed silicon shadow mask-based metal contact patterning process is cost-effective and free from photoresist (PR) chemical coatings and thermal processing. After a detailed investigation, sodium dodecyl sulfate (SDS), an anionic surfactant, along with ultrasonication process, was found to be effective for the removal of unclamped and metallic SWNTs, resulting in aligned and clamped semiconducting SWNTs between the electrodes. The presence of aligned semiconducting SWNTs was confirmed using atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), and Raman spectroscopy techniques. The fabricated devices were tested for nitrogen dioxide (NO2) gas sensing as a test case. The sensitivity enhancement of ∼21 to 76% in the 20-80 ppm NO2 concentration range has been observed in the case of aligned semiconducting SWNT devices compared to the random network SWNT-based sensors.

Observation of a Strongly Enhanced Relaxation Time of an In-situ Tunable Transmon on a Silicon Substrate up to the Purcell Limit Approaching 100 μs

The remarkable advances of quantum computation technology with superconducting qubits based on circuit quantum electrodynamics (QED) architecture have been achieved by improving control, protection and measurement of the quantum states at the same time. At the heart of all these quantum operations, the significant enhancement of the qubit coherence time during the last decades was the key. Even after all these advances, the coherence and relaxation time of superconducting qubits still requires further improvements toward fault-tolerant quantum computation. Here, we report our observation of a strongly enhanced lifetime of an in-situ tunable superconducting transmon qubit on a silicon substrate that is embedded in a three-dimensional copper cavity. We measured a lifetime of the qubit of up to 84 µs, which is the best reported value of an in-situ tunable transmon on a silicon substrate. In our experiment, the in-situ frequency tunability over a broad range enabled the Purcell factor to be controlled continuously by detuning the qubit frequency against the resonator frequency in the strong dispersive regime. The silicon substrate has its own importance because the substrate should be fully compatible with the conventional semiconductor processes so that scalability and multi-chip module capability are guaranteed. In order to control the Purcell factor with another parameter, we displaced the qubit position in the cavity and observed a longer relaxation time with a smaller coupling coefficient. We believe that this systematic study and the control technique of the Purcell effect in the circuit QED design, together with minimizing the microwave photon loss through an improvement of the fabrication, will contribute to the realization of a practical large-scale quantum computer based on superconducting qubit technology.

Self-Terminated Surface Monolayer Oxidation Induced Robust Degenerate Doping in MoTe2 for Low Contact Resistance.

We introduce an effective method to degenerately dope MoTe2 by oxidizing its surface into the p-dopant MoOx in oxygen plasma. As a self-terminated process, the oxidation is restricted only in the very top layer, therefore offering us an easy and efficient control. The degenerate p-doping with the hole concentration of 2.5 × 1013 cm-2 can be obtained by applying a ∼300 s O2 plasma treatment. Using the degenerately doped MoTe2, we demonstrate a record low contact resistance of 0.6 kΩ μm for MoTe2. Our measurement highlights an excellent stability for the plasma-doped MoTe2. The doped characteristics are robust with no significant degradation even after a one-year exposure to the air. The oxygen plasma doping technique is compatible with the conventional semiconductor processes, which can be utilized to realize high-performance MoTe2 field-effect transistors (FETs) or tunnel FETs in the future.

Toward Valley‐Coupled Spin Qubits

AbstractThe bid for scalable physical qubits has attracted many possible candidate platforms. In particular, spin‐based qubits in solid‐state form factors are attractive as they could potentially benefit from processes similar to those used for conventional semiconductor processing. However, material control is a significant challenge for solid‐state spin qubits as residual spins from substrate, dielectric, electrodes, or contaminants from processing contribute to spin decoherence. In the recent decade, valleytronics has seen a revival due to the discovery of valley‐coupled spins in monolayer transition metal dichalcogenides. Such valley‐coupled spins are protected by inversion asymmetry and time reversal symmetry and are promising candidates for robust qubits. In this report, the progress toward building such qubits is presented. Following an introduction to the key attractions in fabricating such qubits, an up‐to‐date brief is provided for the status of each key step, highlighting advancements made and/or outstanding work to be done. This report concludes with a perspective on future development highlighting major remaining milestones toward scalable spin‐valley qubits.

Design and optimization of tunneling photodetectors based on graphene/Al2O3/silicon heterostructures

Abstract Recent discoveries in the field of graphene-based heterostructures have led to the demonstration of high-performance photodetectors. However, the studies to date have been largely limited to the heterojunction with a Schottky barrier, restricted by an inevitable compromise between photoresponsivity and photodetectivity. Here, a new class of graphene-based tunneling photodetectors is introduced by inserting the Al2O3 tunneling layer between silicon and graphene. The photocarriers can tunnel through the designed insulator layer which simultaneously blocks the dark current, thus maintaining high photodetectivity with desirable photoresponsivity. We further modulate the thickness of the Al2O3 layer to explore the tunneling mechanism for the photocarriers, in which a photoresponsivity of 0.75 A/W, a high current ratio of 4.8 × 103 and a photodetectivity of 3.1 × 1012 Jones are obtained at a 13.3-nm-thick Al2O3 layer. In addition, the fabrication process is compatible with conventional semiconductor processing, providing further flexibility to large-scale integrated photodetectors with high performance.

Double‐sided transistor device processability of carrierless ultrathin silicon wafers

AbstractDouble‐sided metal‐oxide‐semiconductor field‐effect‐transistor processing is demonstrated for the first time on an ultrathin crystalline silicon substrate of 6‐20 μm in a 100 mm diameter wafer format without a carrier wafer, the thinnest free‐standing silicon wafers ever fabricated. The compatibility of the flexible material with conventional semiconductor processing tools is enabled by supporting an interior ultrathin silicon with a surrounding thicker ring of silicon. Current‐voltage characteristics of transistors on ultrathin silicon show performance as expected from bulk silicon, with electron mobility ~1500 cm2 V−1 second−1. Mechanical measurements quantify the handleability.image

Formation of new MXene film using spinning coating method with DMSO solution and its application in advanced memristive device

Abstract Uniform MXene films have been successfully achieved by tuning the process conditions and concentration of Ti3C2 in various solutions. Three different processing methods, i.e. mechanical exfoliation, dipping on wafer, and spin-coating technique, have been investigated in details. In addition, optimized conditions of concentration and dispersion of Ti3C2 in various solutions have been explored as well as spinning speed of spin coater. Next, the physical characteristics of MXene films were investigated and analyzed by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) measurements. Moreover, the MXene films have been introduced into silicon-based devices using conventional semiconductor processing steps. For the first time, two-terminal memristive devices with MXene layers were fabricated. Electrical characteristics has been carefully measured and non-linear I–V behavior with continuous resistance states was observed. This work may pave the way for the applications of MXene in the Non-von Neumann architecture of brain-inspired semiconductor devices and networks.